Evolutionary biology of wood-eating sea urchins (temnopleuridea : trigonocidaridae)

Echinoids comprise a diverse group of Echinoderms composed of around 1000 extant species. The sea urchin family, Trigonocidaridae exemplifies echinoid diversity, being found in almost every marine ecoregion from the intertidal zone to depths over 3,000 m. Some of the Trigonocidaridae are also known wood-eaters, an unusual behavior previously recorded in only three sea urchin species. The family is also characterized by miniature body size and sculpturing of the test. This study is the first phylogeny of the Trigonocidaridae inferred from morphological and molecular evidence. All morphological analyses support the monophyly of the family Trigonocidaridae as well as the monophyly of the clades Trigonocidaris + Genocidaris + Desmechinus, and Hypsiechinus + Prionechinus + Asterechinus (which is monotypic). The molecular analysis does not contradict the morphological analyses and shows strong support for a relationship between Asterechinus and Prionechinus. The evolution of wood-eating and the biogeography of the Trigonocidaridae are explored using this phylogeny.